Indium has been used as a sputtering target for forming a light absorbing layer for Cu—In—Ga—Se-based (CIGS-based) thin film solar cells.
Indium targets are conventionally manufactured mainly according to a melting and casting method. Japanese Examined Patent Application Publication No. 63-44820 (Patent Literature 1) describes a method of forming a thin film of indium on a backing plate, subsequently pouring indium on the thin film to cast indium, and thereby forming an indium target integrally with the backing plate. Japanese Unexamined Patent Application Publication No. 2010-24474 (Patent Literature 2) describes a method of manufacturing an indium target including the steps of feeding a predetermined amount of an indium raw material into a heated mold for melting, removing indium oxide that floats on the surface, cooling the molten indium to obtain an ingot, and grinding the surface of the ingot to obtain an indium target, wherein the predetermined amount of the indium raw material is not fed to the mold all at once but is fed in several divided portions, indium oxide formed on the molten metal surface is removed each time, and then the ingot obtained by cooling the molten metal is surface ground. Japanese Unexamined Patent Application Publication No. 2010-24474 (Patent Literature 2) also discloses that the sputtering target is manufactured via rolling process.